Topics of current studies include: (1) characterization of a new fungal pathogen isolated from a granulomatous lesion of olecranon bursa; (2) Pathogenesis and virulence factor of Candida albicans; (3) biochemical genetics of resistance to 5-fluorocytosine (5-FC) in C. albicans; (4) development of a parasexual genetic system for Torulopsis glabrata. An isolate of Anthopsis deltiodea was found to be the cause of an olecranon brusitis in a man. A. deltoidea has never been reported previously from clinical specimens. A. deltoidea produced dematiaceous hyphae in tissue in the center of the necrotic debris. The relationship between extracellular proteinase and virulence for mice in Candida albicans was studied using an isogenic set of proteinase - producing parent (C9), a proteinase - deficient mutant (C9M1) derived from the parent by nitrouse acid treatment and a spontaneous revertant (C9M1M) obtained by mouse passage of C9M1. The isolate C9 produced a high level of proteinase in vitro and caused 100% fatal infection within 21 days. The mutant produced no detectable enzyme in vitro and all mice survived until day 22. Only 30% of the mice infected with C9M1 died between day 23 and 30. The isolates recovered from the dead mice were found to be proteinase sufficient. The C9M1M produced proteinase in vitro at 44% of the level of the wild type and induced fatal infection in 90% of the mice within 30 days indicating that proteinase activity is one of the factors associated with the virulence of C. albicans. Resistance to 5-flucytosine in C. albicans results from a defect in UMP pyrophosphorylase activity (fcyl) or from a defect in cytosine deaminase activity (fcy2). We have demonstrated complementation in fcyl FCY2 x FCY1 fcy2 crosses. A parasexual genetic system in Torulopsis glabrata was developed by spheroplast fusion between two haploid strains carrying different nutritional markers.